From f470dafddcd688c3ea6031d4bbcbf934fd094711 Mon Sep 17 00:00:00 2001
From: Daan De Meyer <daan.j.demeyer@gmail.com>
Date: Fri, 25 Aug 2023 13:55:36 +0200
Subject: [PATCH] Limit rlim_max in rlimit_nofile_safe() to nr_open

We might inherit a max rlim value that's larger than the kernel's
maximum (nr_open). This will cause setrlimit() to fail as the given
maximum is larger than the kernel's maximum. To get around this,
let's limit the max rlim we pass to rlimit() to the value of nr_open.

Should fix #28965

Conflict:NA
Reference:https://github.com/systemd/systemd-stable/commit/f470dafddcd688c3ea6031d4bbcbf934fd094711

---
 src/basic/rlimit-util.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/basic/rlimit-util.c b/src/basic/rlimit-util.c
index 91424cd3cc..a0ffb24626 100644
--- a/src/basic/rlimit-util.c
+++ b/src/basic/rlimit-util.c
@@ -401,7 +401,11 @@ int rlimit_nofile_safe(void) {
         if (rl.rlim_cur <= FD_SETSIZE)
                 return 0;
 
-        rl.rlim_cur = FD_SETSIZE;
+        /* So we might have inherited a hard limit that's larger than the kernel's maximum limit as stored in
+         * /proc/sys/fs/nr_open. If we pass this hard limit unmodified to setrlimit(), we'll get EPERM. To
+         * make sure that doesn't happen, let's limit our hard limit to the value from nr_open. */
+        rl.rlim_max = MIN(rl.rlim_max, (rlim_t) read_nr_open());
+        rl.rlim_cur = MIN((rlim_t) FD_SETSIZE, rl.rlim_max);
         if (setrlimit(RLIMIT_NOFILE, &rl) < 0)
                 return log_debug_errno(errno, "Failed to lower RLIMIT_NOFILE's soft limit to " RLIM_FMT ": %m", rl.rlim_cur);
 
-- 
2.39.1